Brake Fluid Flush

[Daria]

I just got some synthetic brake fluid and am ready to change the cheap stuff for something good. I’m using Motul RBF 600.

I was on the manufacturer’s website and they recommend not to mix different types of brake fluids together. Does that mean a complete flush?

What’s the best way of going about this? How much fluid will I need for a complete overhaul?

Thanks, Daria

 

[nsxtasy]

I just got some synthetic brake fluid and am ready to change the cheap stuff for something good. I’m using Motul RBF 600.

I assume you are switching from something else to the Motul. Motul is very good.

I was on the manufacturer’s website and they recommend not to mix different types of brake fluids together. Does that mean a complete flush?

You can mix any non-silicone-based brake fluid (non-SBBF) with any other non-SBBF fluid. That includes DOT 3, DOT 4, and DOT 5.1 (but not DOT 5) brake fluids. Motul RBF 600 is a DOT 4 fluid (although its boiling points are higher than the minimums for DOT 5 and DOT 5.1).

That being said, if you want to get the full benefits from the higher boiling points of the Motul RBF 600, you will want to do a complete flush.

What’s the best way of going about this?

The procedure is in the service manual. If you don't already have a service manual, and you plan on working on your own car, you should get one. You can buy one here.

How much fluid will I need for a complete overhaul?

I think a liter or a quart - LarryB, is that correct?

 

[Daria]

Thanks Ken,
I have a service manual. I will do some reading this weekend and if I still have questions, I'll post them monday.

 

[DanO]

some instructions at:

www.danoland.com/nsxgarage/brakes/bleed/bleed.html

DanO

 

[nsxtasy]

some instructions at:

www.danoland.com/nsxgarage/brakes/bleed/bleed.html

Okay, can someone please tell me the difference between "bleeding" the brake fluid and "flushing" it?

I thought bleeding is the process of opening bleed screws to make sure that any bubbles get out of the system, whereas flushing is the process of removing all the old fluid and replacing it with new fluid - which would include bleeding, but requires more steps (and possibly additional tools/equipment?).

Incidentally, in addition to DanO's write-up (excellent, as usual), there are also some tips about bleeding the brakes in the FAQ here.

 

[Daria]

Okay, let me re-iterate what I’m trying to do. I have to remove the existing brake fluid and replace it with new Motul. This can be accomplished in 2 different ways:

1. Keep bleeding the system while adding new Motul fluid (lets say 2 liters of Motul just to make sure the old stuff has been replaced with new). This should be simple and quick since I have speed bleeders.

2. Completely drain the old fluid (now the system is filled with air from the reservoir tank to the calipers) and THEN fill with new Motul.

Looking at the tips about bleeding the brakes in the FAQ, I read “bleeding the brakes never means emptying them”. I’m assuming that this statement is an advice for those who are just bleeding their brakes to remove any small bubbles and does not rule out scheme #2 above.

For simplicity, I like scheme #1, but I’m mixing different types of brake fluid together (contrary what the makers of Motul recommend).

So a question to those who now have Castrol SRF, AP 600 Racing, ATE Super Blue or …. How did you make the change?

... flushing is the process of removing all the old fluid and replacing it with new fluid - which would include bleeding, but requires more steps (and possibly additional tools/equipment?).

I don’t see why I would need additional tools unless I am also flushing the ABS reservoir. I don’t see the need to replace the ABS reservoir with brake fluid having a higher boiling point.

 

[DanO]

A flush is bleeding the brakes until the new fluid appears at the bleed screw. Introducing air into the brake system is generally considered a bad thing so #1 is your answer! 2 liters will be more than enough to get the job done. I used to know the number of pumps required to flush each caliper and I wrote it down somewhere, but I cannot find it!

Obviously, the right rear caliper takes quite a bit of pumps, where as the left front only takes a few, etc. You might be able to tell the difference in color between the old and new fluid or you might not. That’s why ATE Super Blue fluid comes in both blue and gold color—so one can tell when the new fluid has arrived at the caliper.

Here’s what I’d do:
RR Caliper – 20 pumps
LF Caliper – 5 pumps
LR Caliper – 15 pumps
RF Caliper – 10 pumps
Repeat 3-4 times or until out of fluid. Leave fluid level in the reservoir approx. where you found it before starting the procedure, probably somewhere between min and max mark.

Be careful not to depress the brake pedal too far (not too much past ½ way) when bleeding as it can sometimes damage the seals in the master cylinder. Some people place a block of wood behind the brake pedal to keep it from going too far. Honestly, I’ve never been too concerned with this because I try to keep fresh fluid in my brakes all the time but if your fluid hasn’t been flushed regularly then it’s possible that there may be some buildup of deposits in the master cylinder just beyond where the seals normally stop during regular braking and if you extend these seals beyond this point when bleeding then they might be damaged when breaking through the deposits…so the theory goes.

Good luck,
DanO

 

[aerodrums]

BRAKE FLUID FLUSH

GREAT INFO FROM THE “PRIME”


I remember reading that one should NOT mix the types of fluids between the two systems. Maybe DANO will address this question; Is the ABS system to have the same type of fluid as the normal system??

Many nsx’er change both systems to the same type fluids.

It sure pays to do it right the first time!!

DAVE.

 

[hlweyl]

I just got some synthetic brake fluid and am ready to change the cheap stuff for something good.

Is "cheap stuff" referring to the Honda brake fluid? I've been under the impression that Honda brake fluid is a very good product. Those that have changed brake fluids, did you have a problem with Honda brake fluid? Or are you changing just for the track?

Enlighten me please.

 

[DanO]

The ABS is a separately contained system. Fluids between the ABS and the regular braking system do not interact. It is important to flush both at the scheduled interval but they do not have to be done at the exact same time or with the same fluid.

As long as the Honda fluid is DOT 3, DOT 4, or DOT 5.1 (see Ken’s post above) then it should be just fine for street driving.

DanO

 

[Daria]

Re: Re: Brake Fluid Flush

Those that have changed brake fluids, did you have a problem with Honda brake fluid? Or are you changing just for the track?

I have upgraded my braking components and am also changing the brake fluid for track use - no problems with Honda fluid.